1. Field of the Invention
The present invention relates to a magnet device with double fixing positions for changing the magnetic circuit, and more particularly to a magnet device which can be applied to electromagnetic valve, solenoids, relays and etc. and whose both sides make use of the magnetic force to produce the holding force without using spring to produce a reverse holding force. Accordingly, the position of the iron core can be changed without continuous supply with electricity so that a an over-heated state through a long time use can be prevented to burn down it and the electricity is therefore able to be saved.
2. Description of the Prior Art
The notions of magnetic force was got from the natural magnetic stone which attracts iron slag without magnetization, and the position attracting slag most is called magnetic pole. In respect of the earliest scientific research on the magnetic phenomena, it was performed by a Dane, Hans Christian Oersted, in 1819 who first found the magnetic needle will be deviated when it comes near to the connection wire supplied with electricity.
It was known by research afterwards that the magnetic field hat lines of force. FIG. 14 shows that the lines of force extends from the N pole of a magnet through air to an S pole while FIG. 15 shows that the field is formed because the wire is wound to be solenoids and is supplied with electricity (i), and that the lines of force extends from one end of the solenoid through air to another end, whereby a closed circuit is formed inside of the solenoid. Therefore, lines of force extends from the N pole to the S pole and shows a closed state. Besides, Ampere, a French physicist, found in the beginning of 19 century that the reason of the field created by a magnet is the same to that of the field created by solenoids--that is, he thought that the field effect created by the magnet is resulted from the electric current therein or on the surface.
Nowadays, the magnetic field effect has been broadly applied to the electromagnetic valves, solenoids and relays. FIG. 16 shows a schematic drawing of a conventional electromagnetic valve which makes use of the magnetic force created by a coil 1C, when excited, to attract a iron core 1F to achieve the aim of opening valve 1V. However, the iron core 1F of this kind of electromagnetic valves must be fitted with a spring 1S to provide with a reverse holding force. In order to keep the electromagnetic valves in a opened state, the coil 1C must be continuously excited. As shown in FIG. 17, the magnetic force of the coil is made use to attract the iron core 1F to the right, so that the plastic pad 1P is separate from the valve hole. However, the outward resilient force of the spring 1S will counteract the magnetic force of the coil 1C. Accordingly, increasing power energy is apparently wasted; moreover, that being existed for a long time to attract the iron core 1F can not only waste the power energy, but also make the electromagnetic valves heated, so that a short circuit or burn down is easily caused to bring danger. In addition, the using life is also reduced. This has been disclosed in Taiwan Patent No. 319343, 290615, 115728, 268552, 304570, 155433, 222448, 182896, 212501 and 241854.
The above-mentioned patents have its own advantages and disadvantages. And the common disadvantage lies in that a spring is made use for supplying reverse holding force.